1. Field of the Invention
The present invention relates to a mixing device for mixing raw material (feed) and catalyst in fluid catalytic cracking device (fluidized catalytic cracking apparatus).
2. Description of the Related Art
A fluidized catalytic cracking apparatus is used to efficiently produce gasoline by using heavy oil as feed. An upflow moving-bed reactor in which feed oil and a catalyst (catalyst particles) are supplied from the bottom portion of the reactor to be allowed to flow upward has been used as the fluidized catalytic cracking apparatus. In the upflow moving-bed reactor, since the catalyst and the feed oil are allowed to flow against gravity, a phenomenon of back mixing in which a part of the catalyst flows downward due to gravity is caused. This phenomenon lengthens a staying time of the feed locally, and thereby causing a problem such that a reaction time becomes ununiform.
In the recent years, since a demand for light olefin used to produce chemicals is highly increased, it is required a method for producing as much of the light olefin as possible in the fluidized catalytic cracking apparatus without decreasing the production volume of the gasoline. A downflow moving-bed reactor as described in U.S. Patent Application Publication No. 2001/0000024 (corresponding to Japanese Patent Application Laid-open No. 10-249179) is suggested as an apparatus to meet the request as described above and to solve the problem of the upflow moving-bed reactor. Since the catalyst and the feed are allowed to flow in a direction which is the same as that of the gravity in the downflow moving-bed reactor, the downflow moving-bed reactor has no problem of the back mixing as described above and is capable of achieving a uniform reaction time. In the downflow moving-bed reactor, in order to produce the light olefin more efficiently, it is required to shorten a contact time during which the feed and the catalyst are contact with each other as compared with the case in which the upflow moving-bed reactor is used. Therefore, it is required to mix the feed and the catalyst quickly, and for the purpose of realizing the quick mixing, U.S. Patent Application Publication No. 2001/0000024 (corresponding to Japanese Patent Application Laid-open No. 10-249178) suggests, for example, a mixing device which includes not only an external feed supply unit provided along the outer circumference of a conventional moving-bed reactor but also a feed supply section (internal feed supply section) provided in the moving-bed reactor.
The internal feed supply section described in Japanese Patent Application Laid-open No. 10-249178 is provided with a supply pipe which is inserted into the moving-bed reactor from the exterior of the moving-bed reactor in a horizontal direction and is bent in a vertical direction in the moving-bed reactor (see FIG. 7 in Japanese Patent Application Laid-open No. 10-249178). Since such a supply pipe is provided in the moving-bed reactor, there are problems such that it is not easy to repair and/or maintain a feed injection port provided at the tip of the supply pipe and it is difficult to remove the supply pipe itself having the bend structure as described above.
In view of the above, an object of the present invention is to provide a mixing device for a fluidized catalytic cracking apparatus which has a simple structure without an internal feed supply section and which is capable of realizing an efficient mixing equivalent to a case in which the internal feed supply section is provided.